The present invention relates to an auxiliary drive for a trailer. Such an auxiliary drive, for example for a caravan, is generally known in the prior art. It has long been a recognized problem that after uncoupling from a towing vehicle, manoeuvring of heavier trailers in particular constitutes a problem, which can be solved by using relatively small electric motors, which drive the wheels of the trailer. In the prior art the use of drive rollers that are connected to the electric motors and engage the tyre of the wheel is generally proposed.
The problem is, however, that considerable pressure forces are necessary to prevent slipping between the drive rollers and the wheels. The fact is that driving of the wheels is required most in difficult circumstances in which such wheels are on soggy ground or the like, when the grip between wheel and drive roller will also be far from optimum.
It is felt by some that the pressure of the roller against the tyre can cause damage to the tyre in the long run. Moreover, such a drive is easily damaged. For that reason, British Patent Specification 2,305,408 proposes a drive in which the brake drum of the wheel is provided with a ring gear, and an auxiliary shaft extending parallel to the wheel axle is present. The auxiliary shaft is provided with a gearwheel on both sides, which gearwheel engages with the abovementioned ring gear, on the one hand, and with an auxiliary drive lying inside the chassis, on the other hand. By movement in the axial direction, engagement or disengagement can be achieved.
Such a structure avoids the problem of failing contact between roller and tyre, but it has the disadvantage that such a system is not easily universally usable. Moreover, the position of the spring-loaded wheel relative to the chassis constitutes a problem for the positioning of the auxiliary drive.